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ADDRESS: 

BY THOMAS ANTISELL, M. D., PROFESSOR OF CHEMISTRY TO THE MEDICAL DEPARTMENT 
OF GEORGETOWN COLLEGE, D. C. 

ON THE RELATIONS OF PHYSICAL GEOGRAPHY TO AGRICULTURE. 

{Delivered at the seventh annual meeting of the U. S. Agricultural Society.) 

The scope of Ph3'sical GeogTapliy is so ample, aiming to exhibit the heap 
of special knowledge gathered by descriptive geography, so as to constitute 
a harmonious whole, (allied by numerous relations and subordinate to the 
general scheme gf the universe,) that it would be impossible to do more 
than bring a small portion of that information before you this evening. 

My object, on this occasion, is to show how necessary an aid to agricul- 
ture it may become, by pointing out the close connexion which exists be- 
tween the coast conformation and the altitude of this continent; between 
the trend of the mountains and the direction of the winds which pass over 
the whole surface. 

Ph3^sical Geography may be described as involving a general description 
of the earth's surface; not in regard to man in his social and political rela- 
tions, (this being descriptive geography,) but with reference to all mutual 
relations of matter and vitality on the globe. It comprises a very large 
and important part of an universal knowledge of nature; treating of the 
forces by which our globe is affected; of the atmospheric veil which is hung 
around bur globe, and its varied appearances ; of the vast ocean which 
covers so large a portion of the solid surface with an uniform fluid; of the 
way in which the land is distributed; the disturbances and alterations to 
which it is subject; the mode in which it has been elevated; and the natural 
families, both animal and vegetable, which exist upon it now or have existed 
in times gone by. It is in line a combination of various observations, and 
an attempt to establish unity among a vast quantity of phenomena. 

The importance of the study of Phj'sical Geography' lies not merely in its 
relations to agriculture, but also as forming a part of the history of our 
globe, which introduces to our view the preadamitic day when the sun shone 
and the earth did not regard it; when the seed-time and harvest of nature 
were in perpetual action; and when solar or external warmth was, if felt, not 
felt as that impetus to growth and awakening to vegetable life which was pro- 
duced wliolly by the increased and self-sustaining temperature of the crust of 
the globe ; of the long epoch which elapsed until refrigeration was sufficient to 
allow of the perception of seasons, and during which period no wintry hand 
was held forth, at periodic intervals, to chill the operations of vegetable life. 

The study of the ancient physical geography of the continent has been 
forced upon us by the advance of geology. 



The Relations of Physical Geography to Agriculture, 



The present valley of the Mississippi was at no distant period (geologi- 
cally speaking) occupied by an arm of the sea of considerable breadth, wash- 
ing the base of the Rocky mountains on the one side and the Alleghanies on 
the other, and extending north or northwesterly by the present position of 
the larger lakes, and terminating by joining the great northern ocean. Our 
present continent consisted then of two islands, or groups of islands, running 
north and south, placed alongside this middle sea, and possessing an abun- 
dant flora of a warm and insular climate. The extent of the coal-beds and 
their position so far to the north of districts which could now sustain con- 
generic species shows at the same time the luxuriance of vegetable life and' 
the change which the climate has undergone. In the early tertiary beds we 
have for the first time the cognizance of the occurrence of a winter, and also 
that of a gradually shallowing sea. The islets on each side gradually and 
slowly emerging, and forming ultimately a connected mainland, and oblitera- 
ting the connexion between the cold and warm oceans, leaving our noblest 
river as the poor representative of the primitive sea. 

This change of level, which made our continent one and entire, must have 
entailed a considerable change in the climate, of which the tertiary winter 
was the first appearance. The current which flowed originally through the 
internal sea passed toward the North, carrying the warm waters of the 
tropics towards the poles. The Gulf Stream, as it was, flowed along this 
channel and carried the warmth and vapors through the heart of the conti- 
nent, and thus elevated its temperature far above its present level. This 
difference of temperature may of itself almost have been sufficient to allow 
of insular or tropical vegetation flourishing in high latitudes. 

As the elevatiomof the land and consequent shallowing of the sea was 
very gradual, so must also have been the lessening of the temperature, and 
the occurrence of those extremes of heat and cold which characterize conti- 
nents having extensive plane surfaces fronting- to the North. 

Unappreciable in a single generation, or perhaps many successions of 
them, it has yet made wonderful changes in the flora and fauna of the coun- 
try, whose dependence for existence on temperature is so inevitable. 

Looking upon our globe not as an inert, stationary mass of matter, but as 
constantly in motion, a motion not confined to it as a mass, but extending 
to its most internal particles, so that at no one period can we say of them 
that they occupy the same position they did the instant before, as exposed 
to various influences and reacting on its various parts, we have placed before 
our consideration many problems of deep and lasting interest. 

And since the occupation of those whom I have the honor to address is 
connected with the surface of the earth and the changes by which it is 
affected, no apology, I am sure, is necessary from me when I endeavor to 
recapitulate some of the results of these reactions produced upon a larger 



By Doctor Thomas Antisell. 



and grander scale than the eye of a sing-le observer can take in, and, view- 
ing theni in a more general way, mix a little philosophy with our every day 
work. 

[Dr. Antisell exhibited four sections of the continent made on an extended 
scale, (40 miles to the inch,) which showed the altitude of the continent 
along several parallels, the vertical scale being at the rate of 1,200 feet to 
the inch. The line of the four sections ran as follows: 

Section 1 lies between latitude 44° and 48° north. The length of this 
portion of land is abeut 3,200 miles from Puget Sound to the shores of 
Maine; it crosses the Cascade mountains, the Valley of the Columbia and 
Spokane rivers, the Bitter Root and Rocky mountains, to the Milk River 
valley; touches the Missouri, and reaches the Mississippi at St. Paul's; 
thence to Chicago and along the frontier. 

Section 2 lies between latitude 38° and 41° 36'. The length of this sec- 
tion is about 2,600 miles from the Pacific shore north of San Francisco, 
California, to Council Bluffs, and thence to the Atlantic about parallel 40°; 
crosses the Sierra Nevada, Humboldt River valley and mountains. Salt Lake 
Valley, Wahsatch mountains, Green River valley. Park mountains; thence 
along the Platte, Kansas, and Missouri rivers to St. Louis; finally to the 
Atlantic along latitude 39°. 

Section 3 lies between north latitude 33° 43' and 35° 59'. Its length is 
about 2,400 miles. Commences on the Pacific ocean at San Pedro, crosses 
the Sierra Nevada, and enters the Mojave valley and tlie mountains sepa- 
rating it from the Colorado valley; tlience up Bill Williams's fork to the 
valley of the Colorado Cliiquito ; thence to the headwaters of the Rio 
Grande, across the Pecos, to the Canadian, and down it to Preston, and 
thence to the Atlantic ocean along latitude 36°. 

Section 4 lies between latitude north 32° on tiie western shore and 29° on 
the eastern shore. Its length is about 1,800 miles. This section commences 
at San Diego, on the Pacific shore, crosses the Sierra, the Colorado desert 
and river, ascends the Gila, crosses the region of mountains, basins, and 
strikes the Rio Grande at El Paso; thence southeast over the margin of the 
Llano Estacado to San Antonio, Texas, and terminates at Indianola, on the 
Gulf of Mexico.] 

We will now consider the configuration of our continent. The sections 
showing the elevation or altitude of the continent above the sea level, 
which (we shall not now examine further) were obtained by the surveys 
made in the Pacific railroad examinations, indicate to us how greatly 
the country is exposed on the north to the fierce action of polar winds. 
An extensive plain north of 60°, sloping down to the Polar sea with its 
level, interrupted only by the chain of the Rocky mountains, terminating 
at the mouth of the Mackenzie river: this mountain range, although 



4 — The Relations of Physical Geography to Agriculture, 

deranging the level, is no protection from northerly winds, wliich, ascending 
the gentle slope of the continent and taking the same or a similar trejid with 
the mountain chains themselves, pour their immense volumes of dry and 
chilled air over the middle portions of the continent, reaching to the shores 
of Cuba. In 42° north latitude the continent gradually increases in alti- 
tude, owing to the development of parallel chains and the formation of a 
great plateau upon which these chains are figured — a plateau which drops 
both north and south — is bounded abruptly by the Sierra Nevada on the 
west side, and drops slowly down on the east to form the Mississippi valley. 
The sections presented illustrate this plateau and the mountain chains. 

The eflect of this geographical configuration is to give tlie continent a 
climate of extremes, and, by its increased summer temperature, to allow the 
development of a larger number of species of plants toward the north than 
could occur if transverse mountain chains were spread across the continent- 
The extreme cold of winter is produced by a combination of several causes; 
such as — 

1st. The small quantity of land in the torrid zone, 

2d. The Rocky mountain range and Sierra Nevada. 

3d. The expansion of the continent to the north and northeast. 

4th. The warmth of our tropics being carried away towards Europe by 
the Gulf Stream. 

5th. The cold current of ice-water flowing close to our east shore. 

While our summer warmth is produced by the southwest wind flowing 
over the southern slope of the continent, and running up the Mississippi 
valley to latitude 52° north, where its influence is distinctly felt in the 
valley of the Saskatchewan. 

A continent whose pi'ojection and elevation is thus given to us must have 
a very different distribution of warmth over its surface from one in which 
transverse chains check the flow of both northern and southern breezes. 

The meridianal disposition of the mountains allows the north winds to 
blow with unmitigated force, and also permits the warmer southeast wind 
to force its way northwards along the funnel-shaped valley of the conti- 
nent, the effect of which is, that when such vv^inds are prevalent, (as in sum- 
mer,) the warmth is carried further north than it is either in Europe or Asia, and 
hence in the same latitudes the climates of continents differ, and even on 
the same continent the difference is great; so tliat lines of latitude give us 
no exact idea of climate. 

In Europe, where the Alps, Pyrenees, and Carpathians form a barrier 
from east to west, the African winds are arrested or diverted from their 
northerly course by the mountain barrier, and the summer warmth of the 
Baltic Coast is not equal to that of the same latitude on this continent. 
The northern limit of maize in Europe is in latitude 41°, on this continent 



By Doctor Thomas Antisell. 



it is cultivated in latitude 54°, or seven degrees more to the north; the ex- 
treme limit of wheat growth is near Edinburgh, in Scotland, while it grows 
well 4° further north in the Saskatchewan Valley. 

To Humboldt is due the merit of being the first to draw upon the map of 
the Globe lines of equal temperature, which represent an equal annual 
warmth everywhere over which it passes, these lines are always curved 
and might be termed climate lines, but have been called by their proposer 
by the name of isothermal lines. Were the surface of the Globe even, 
without any irregularities or local deposits of water, or were the Earth of 
an uniform nature so that absorption and radiation might go on equally Avell 
everywhere, then lines of latitude would convey to us all the information 
of the climate we need possess, but this is far from being the case. There 
are many disturbing causes which go to make a curve, of which the chief 
are, the influence of the currents of air and water, and the variations of the 
curve thus formed is due to local causes, such as mountains, valleys, &c. 

The territory of the United States, is mostly included between the iso- 
thermals of 42° and 10° which usually are curves of a large circle extending 
nothward from the sea-coast on either side, but suffering a great deflection 
southwards where they cross the Rocky mountains. The western or Pacific 
termination of the curve is placed many degrees to the north of the eastern 
limit, owing to the cooling influence of the icy stream which flows south- 
ward along the New England coast reducing the temperature of that shore. 

As we approach the tropics the lines of mean annual temperature run 
nearly parallel to one another, and of countries situated within these circles 
we might (knowing the mean temperature) be able to declare the char- 
acter of its Agriculture In fact the temperature- of each day differs little 
from that of the entire year, during which period vegetable life proceeds 
without interruption. It is altogether different with regard to places out- 
side of these zones. The mean annual temperature alone woidd give us 
no correct idea of what plants might be cultivated, since it gives us no 
information what the variation between summer and winter temperatures 
may be in any place under these lines ; and while the mean annual tem- 
perature of two places might be alike, the warmth of the summer might 
present a remarkable contrast; hence, lines of mean temperature for the 
several seasons were required, and of these that of summer and winter is 
especially demanded by Agriculture; these lines are termed iso/Aera^ and 
isochimenal. 

In applying our knowledge of isothermal lines to agriculture, this fact 
must be borne in mind, that it is the isotheral line, or the line of mean sum- 
mer temperature, which is of chief importance; in other words, it is the 
mean summer temperature, or the mean temperature of the time during 
which the plant is growing, which is of importance, and as most of the 



6 Tlie Relations of Physical Geography to Agriculture, 

plants which are cultivated for food are annuals, this becomes an important 
consideration. 

The question, can a plant grow or be cultivated in a certain latitude, is 
answered approximately by determining the warmth or mean temperature of 
that place during the season of growth. 

To Boussingault are we indebted for the first clear insight into the im- 
portance of knowing summer temperatures; he showed us that by inquiring 
what time elapses between the sprouting of a plant and its maturity, and 
then determining the temperature of the interval which separates these two 
periods, we learn that each species of plant requires for its maturity a cer- 
tain amount of heat, (which may be measured by the degress on the ther- 
mometer ;) that no matter where the plant is grown, this temperature is 
attained; if grown in colder locations, the exposure of the plant to the sun 
must be prolonged in a corresponding degree; in other words, the number of 
daj's between the germination of the seed and full ripening of the plant vary 
with the temperature, in order that the plant may receive its due share of 
heat. 

Hence if we multiply the number of daj's which a given plant takes to 
perfect its growth in different climates by the mean temperature of each, we 
obtain numbers very nearly equal. Thus for Indian corn, we find that in 
order to ripen it takes an exposure equal to 7,000° to 8,000° of Fahrenheit, 
and for wheat it does not much exceed 1,200° Fahrenheit. In Wisconsin 
and the State of New York wheat requires from 7,200° to 7,600° of heat, 
and 122 days for growing, the mean temperature being 67° Fahrenheit. In 
Venezuela wheat ripens in 92 days, with a mean temperature between 75° 
and 76° Fahrenheit, which gives 6,918° Fahrenheit. At Truxillo 100 days 
mean temperature, 72° 1' Fahrenheit, which is equivalent to 7,210° Fahren- 
heit. In Costa Rica it does not require more than 69 days to ripen, with a 
mean temperature of 81°, which gives 7,209° of warmth. These instances 
show the total absolute warmth which a plant requires to be exposed to for 
ripening. 

M. Ad. De Candolle has applied this process of calculation of Boussingault 
to explain the limitation of species of plants toward the north of Europe 
with considerable success, and has shown that for wild plants as for food 
plants thei-e is required a certain mean temperature under which only they 
can grow and propagate. But all these conditions of mere warmth would 
be lost upon our continent, and rendered useless as regards the growth of 
plants if moist winds cannot freely blow over the soil. The tropical winds 
which flow along with the equatorial current of water send a part of their 
mass along the Rio Grande and Mississippi valleys northward, dropping its 
moisture as it passes north, and spreading itself laterally so as to cover the 
whole east of the continent. As might be supposed, the largest quantity of 



By Doctor Thomas AntiseU. 



rin occurs upon the first land over which it flows, so that about eighteen to 
twenty inches are deposited in summer in Louisiana, Alabama, and Florida. 
The fall of rain gradually lightens as it reaches higher lands, until it is con- 
fined solely to the mountain chains, the valleys being passed over without a 
shower, and this continues until the ocean wind loses all its excess of mois- 
ture, and even the mountain summits theijiselves receive but a scanty supply. 
Hence it happens that the great sloped plateau east of the Rocky mountains, 
and the upland plains and valleys of New Mexico, arc so sparingly supplied 
with herbage as to resemble a desert. The atmosphere of the Gulf, so loaded 
with moisture at starting northward, has, by the time it reaches latitude 38° 
and 40° in that elevated region, lost almost all its watery vapor. Having 
now ascertained that moisture and warmth are essential to plant growth, 
we have yet to learn that a fall of rain over a district docs not always imply 
fertility. In order to insure harvests, it is no immaterial thing when the 
rain should descend. Summer rains fall over the deserts of Arizona and 
East California, but they do not render it fertile, nor do the autumnal rains 
of a part of Texas prove sufficient for the wants of Agriculture; for these 
rains must fall in such quantities as will produce fertility, and about the 
time when the crop is being sowed, and during its growth; that is, it must 
have both spring and summer rains. A fair amount of rain in these seasons 
will give us (other things the same) abundant crops from annual plants, but 
this would not be sufficient for the growth of trees; these having their roots 
further in the ground, require that the nutritious matters in the earth should 
be supplied to them by a moist soil, a soil well saturated with moisture, 
which can occur only at seasons when the heat of the sun upon the earth is 
diminished and evaporation is going on more slowly, which process allows 
the moisture to pass downward to the rootlets. To produce a growth of 
trees either winter rains or the melting of winter snows is required. This 
is a point which has not been dwelt upon by writers. 

This prime necessity for winter moisture which trees require leads me to 
make an observation on the cause of our western prairie lands. Prairies 
have been attributed to many origins, among which the frequent burning of 
the woods is deemed by many to be a sufficient cause. Mr. Ruffin, in his 
Essay on Calcareous Manures, with a pardonable zeal in the cause of lime, 
attributes the presence of a prairie to the absence of carbonate of lime in 
the ground, and Mr. Russell, a Scotch meteorologist, (whose views arc 
worthy of being treated with consideration,) thinks that the limits of forest, 
and the cause of prairie land, to be due to an alteration in the physical char- 
acter of the soil, by which its surface and subsoil becomes unfitted for the 
spreading of the roots of the tree. I am not aware that this altered char- 
acter has been noticed by other observers, but that the cause of prairie land 
is mainly due to the limited fall of rain, especially in the winter season, is, 
I think, susceptible of some demonstration. 



8 The Relations of Physical Geograjohj to Agriculture, 



It is well known that the further west we proceed on the other side of the 
Mississippi, the more the trees diminish in number, until ultimately they dis- 
appear from the table land, being found only in river bottoms or on mountain 
sides ; west of longitude 100° in the United States, trees are but sparsely 
found; in Texas a long and tolerable wide belt of oak denotes the western 
limit of trees. The burning of forest timber growth will no doubt repress 
its annual growth and may be the cause of the local prairies of Indiana, 
Missouri, and other States, but can in nowise explain the fact that the whole 
eastern slopes which skirt the base of the Rocky mountains are treeless. 
Neither Indian nor buffalo could have rendered it treeless. If we take the 
meridians between 90° and 100°, as being those where forest vegetation 
ceases to flourish and ascertain the fall of rain during three seasons of the 
year (the fourth not being material to our purpose) we find it to be thus : 



Amount of rain-fall- 



Along parallel 50 
Along parallel 45 
Along parallel 40 
Along parallel 35 
Along parallel 30 



Winter. 



Inches. 

2 
2 to 3 

2 to 7 

3 to 7 
5 to 18 



Spring. 



Inches. 
6 
6 
10 

11 to 12 

12 to 14 



Summer. 



Inches. 
8 to 10 
8 to 12 

10 to 14 
8 to 15 
8 to 20 



Where two quantities are given under one parallel the left hand figures 
refer to the western portion (100°) and those on right hand to the eastern 
longitudes (90°) of the district in question. Let us select parallel 30° in 
winter ; we find its western limit to receive not more than 5 inches of rain. 
What portion of the 5 inches will sink into the east and become available 
for tree growth ? It may be stated in round numbers that in the latitude of 
30°, onc5"ourth of the winter rain-fall may sink six feet deep into the soil; this 
would give us U inch of rain on the west side, and 4i inches on the east 
side of the district. The former quantity appears just sufficient to develop 
the growth of trees, but not to sustain a forest. Masses of trees do not ap- 
pear until we get east of meridian 90°, where the winter rain-fall is much 
higher than in 100°; passing north along this meridian we find in latitude 
35° the rain-fall of winter to be 3 inches, giving in that latitude six-tenths of 
an inch of rain for soakage. This is not sufficient for timber growth, and 
accordingly trees disappear. This probably then is the point of limit of 
tree growth : a rain-fall in winter equal to five inches. If we construct a 
hyetic line of five inches we would find it to stretch from the Sault Saint 
Marie, by Milwaukie, S. W., to the Rio Grande near its mouth ; to the west 
of this line the fall varies from 2 to 3 inches. South of 40° latitude, not 
many forests are found west of the curve, until the highlands of New Mexico 
are reached. At the headwaters of the Rio Grande and along the Rocky 



By Doctor Thomas Antisell. 



mountain chains and plateau between 105° and 110° longitude, the fall of 
winter rain rises to 5 inches and trees reappear. In northern Sonora, in the 
valleys of the Great and Little Colorado, in the Great Basin, to nearly as 
far north as Humboldt river, in Arizona, and the southern part of New Mexico, 
and in northwestern Texas, the fall of winter rain does not exceed one inch, 
and trees do not occur in the lowlands. 

In northern latitudes, where evaporation is much less, of course a lesser 
rain-fall sufffces ; but this does not affect the general statement made that 
the cause of prairies or absence of timbered land is due to insufficient rains 
during the season of least evaporation. The numerical statistics and the 
growth of timber here pointed out must stand in the relation of cause and 
effect, and then is rendered more probable by refiu'ence to other countries 
tiian our own. 

We see analogous instances of the dependence of growth of trees upon 
the amount of moisture in the soil, in the case of the pampas of South 
America, where there is a loose sandy soil impregnated with saline matter, 
and inimical to vegetation as it exists; this tract, called the Traversia, 
when assisted by irrigation, is the most fertile soil imaginable, (Malte Brun.) 

The Steppes of European Russia, and of northern Asia, are not morasses 
or low and watery places, but, on the contrary, dry, elevated, uninhabited 
plains, because destitute of trees and water. 

Having placed this theory now permanently before the public, I leave it 
for the criticism of the well-informed, and will return to consider the results 
of warmth and moisture as regards agriculture as an art. The effect of 
these two agencies combined is to produce fertility in soils of normal com- 
position. 

The rapid partial exhaustion of some of our eastern lands has led to a be- 
lief that our soils are not as lasting as those of Europe, a belief which has 
no reasonable foundation. We do not know what the productiveness of the 
virgin soils of Europe first were; but cultivated imperfectly as they have 
been for two thousand years, they still yield abundantly, and they will ever do 
so so long as they possess depth and obtain moisture sufficient to dissolve sol- 
uble matters. The question indeed may be asked, can a soil be exhausted 
so as to be worthless? that is to say, a soil originally deep and rich. Ex- 
perience gives us the answer in the negative. The plains of Egypt, still 
fertile, have been cultivated for four thousand years; the valleys of Arabia 
for nearly as long; the grapes of Canaan are as large and as luscious as in 
the days of Joshua. The plains of Greece, Troy, India, and China, cultivated 
for>te*rthousand generations, still retain their fertility. No proof lias been 
/yet afforded of sterility occurring on a large scale; partial exhaustion may 
indeed occur, and may be as easily overcome by the efforts of one or two 
generations. Are our lands inherently worse, less fertile naturally than 



10 The Relations of Physical Geographij to Agriculture^ 

those of the eastern continent, that we are compelled after a hundred years 
of cultivation to go further westward, in fact to become century noihads, and 
fill up the Mississippi valley at the expense of the population of the Atlantic 
States^D 

From what has preceded, it is evident that if the summer temperature be 
increased and accompanied by moisture the productiveness of such region 
is increased. Indeed it is to some extent in the power of each farmer to ele- 
vate the temperature of his land by good cultivation. As an example of 
what may be accomplished in the way of elevating the capability of soil, 
the efforts of Mr. Coke, of Holkham, (afterwards Earl of Leicester,) maj^ be 
instanced here. When he commenced the management of his estate, his first 
agricultural adviser was a Mr. Overman, of Dutch descent, one well ac- 
quainted with the evil effects of raising wheat crops in succession. The 
heads of the covenants of all leases made by Mr. Coke were drawn by Over- 
man, and only restrained the tenants from cultivating two consecutive corn 
crops, (wheat.) Working on this plan, Mr. Coke, by his turnips and sheep 
raising, so raised the fertility of his land that in 1850 the second Earl en- 
couraged his tenantry to return to the once justly condemned system re- 
ferred to, for the reason that the soil, which in HtO had been exhausted, had 
in the course of eighty years, through high farming, become almost too 
fertile. 

The whole history of Coke's farming shows to what condition a soil may 
be brought with profit to the proprietor, for the first Earl made a princely 
fortune before his death. When he succeeded to the estates of Holkham, the 
old mansion of the Leicester family lay in the middle of a tract, almost a 
desert, an uncultivated heath in Norfolk. The last Earl, speaking of the 
poverty-stricken and deserted condition of the land, used to say that his 
nearest neighbor was the King of Denmark, and his father described the 
sterility of portions of the surrounding property by the remark "that he 
found two rabbits quarrelling for one blade of grass." By his extensive 
growth of turnips, the use of drill liusbandry, his improvement in stock, and, 
above all, the introduction of the use of oil-cake as food, he has materially 
improved agriculture. This latter event was in 1824. At that time four 
year old mutton was deemed the proper age for being slaughtered. By rape- 
cake and turnips the growth of the animal has so increased that two year 
old sheep are scarce in the market — the majority being only a twelve-month 
old. 

A little of such practice applied to our tobacco lands would bring them 
again into valuable condition, and impress on our minds the double -truth 
that while all profits of agriculture are made at the expense of the fertility 
of the soil, that loss of fertility can always be restored at will. 

The estimate of the fertility of a soil is only true when latitude and climate 



By Doctor TJiomas Antisell. 11 

are taken into account; a more genial sun in summer, a greater supply of 
rain in the growing season, more than compensates for a poorer soil. 
Perhaps we are not yet in possession of all the influences of meteoric agencies 
in producing rapid and abundant plant growth. 

Our ideas of the richness of soil arc derived very much from works 
published in England and northern Europe; but the conditions of climate so 
modify the growth of vegetation that we may overestimate a soil or its 
influence; sunshine and rain occasionally form a substitute for density or 
chemical constitution. 

European observers, looking at the soil of New York or Ohio, on which 
wheat is now grown abundantly, would at once unhesitatingly pronounce 
the attempt to reap a crop on such land an absurd one; because on similar 
lands with their summer warmth no heavy crop could be raised. 

The soils of New England would in Europe be considered sterile clays 
and sands, so that in fact, I am inclined to think that the chemical nature of 
a soil is of less importance than its physical character; that its color, 
consistence, and porosity, are more essential than an abundant supply of 
soluble salts in the land. Dr. Lindly, no mean authority, considers the 
growth of trees, especially of the forest kind, to be determined wholly by 
the texture or rather physical qualities of the soil. We need constant 
and repeated experimenting; no general rules or laws can be, as yet, laid 
down, agriculture having been so recently followed as-a skilled art, not more 
than three or four generations having passed away since any improvement 
was introduced. 

The advances made in agriculture in the last twenty-five years are the 
adoption of drill husbandry, and of drainage, the use of guanos, and 
fertilizers, and an acquaintance with the values of food. Still greater 
improvements are to be hoped from the future. 

Since physical geography thus shows us how a plant is limited by the 
reduction of the summer temperature, and that limit extended as the soil is 
warmed, and since our own experience shows us that soil^^e?' se may have 
very different values, when exposed to different climates, it becomes a 
desideratum to increase the warmth of our soils, by those efforts which we 
know will most effectually accomplish that end, by letting the water out and 
the air in, by the adoption of drainage and irrigation. 

Agriculture when compared with the capacity for progress shown by the 
other useful arts, is placed in a very peculiar position, and the approach to per- 
fection surrounded by many difficulties; the limits of progress are fixed and 
inalterable. The problem which the farmer has to scjlve is not simply how 
to produce the greatest amount of food for man or beast, but how to produce 
it from a given area of the soil. The manufacturer may increase his produce 
by adding to his building and machinery, but the great agricultural machine 



12 



TJie Relations of Physical Geography to Agriculture, 



coimot be extended at will. The farmer is therefore in the condition of a 
manufacturer, who is unable to increase his factory and who must endeavor 
by a higher speed to obtain from it a greater profit. Like such a manufac- 
turer he is forced to adopt new processes which save mere labor directly, and 
produce larger returns. * He is obliged to call upon knowledge to assist 
him, and among those branches which have been less trodden for his benefit, 
and which also would be of incalculable service to agriculture, physical 
geography must be reckoned and placed in the first rank. 



* Professor Anderson in Transactions of Highland Society of Scotland. 



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